This protocol will evaluate the safety and biologic efficacy of repeat administration of the recombinant adenovirus vector AdgvCFTR.10 to the airway epithelium of individuals with cystic fibrosis. Key elements of this study are: administration of the vector to more localized areas of the airways, more careful definition of the pharmacodynamics of expression of the normal CFTR cDNA, evaluation of this expression following repeat administration, and use of a more active promoter/enhancer in the expression cassette.